SOURCE: GDP: U.S. Department of Commerce, Bureau of Economic Analysis as cited U.S. Department of Transportation (DOT), Bureau of Transportation Statistics (BTS), National Transportation Statistics, Tables 1-35 and 3-10, available www.bts.gov as of April 2016. VMT: DOT, Federal Highway Administration as cited in DOT, BTS. National Transportation Statistics, Table 1-35. Available www.bts.gov as of April 2016.